The combination of structural elements and materials called structural system. the structural system may be composed of one or more of the four basic types of structure:
Truss used for structure with large span where the depth is not important. a truss consists of slender elements, arranged in a triangular shape, planner truss refers to truss where all elements lie in the same plane frequently used for bridges. space truss is composed of elements extending in three dimensions. Truss converts loads that cause truss to bend into tension and compression forces. due to this advantages truss used fewer materials compared to beam, also it is composed of slender and long elements, Truss can be used to cover spans from 9m(30ft) to 122 m(400ft).
2. Cable and arches
Cables are used to support long span where the using of truss is not feasible and could lead to a significant increase in cost and size of structure, cables carry the loads in tension and it can be used for spang longer than 46m(150ft), cables used in bridge structures, using of cables is limited by their sag, weight, and method of Anchorage.
Arch carry the loads in compressions, the arch should be rigid, in order to maintain the rigidity and shapes, secondary loading involves shear and moment will generate, these secondary loading shall be considered in the design, arch’s frequently used in bridges and dome roofs.
Frames are used in building, frames composed of beam and column, beam and column may be connected using a pin or fixed connection, frames extended into two or three dimensions, for rigid joint connection the structure known as indeterminate. the loading will cause the frame member to bend and deform, deformation magnitude will depend on the applied load and member properties.
4. Surface structure
The surface structure is made from materials with small depth compared to other dimensions, surface structure can be a tent or inflated structure, for both cases surface material act as a membrane that is subjected to pure tension. also, it can be made from reinforced concrete, it can take the shape of a folded plate, cylinder, etc. this structure will resist load through tension and compression with a little bending.